VX commodore overheating?

[GMMAD]

I had one in a few weeks ago it corroded all the fines off the water pump
still ran cool most of the time only heated up once
the owner came in complained of the heater not working

[Madhatr]

Is it using water at all and have the customer been checking levels regularly and not just the overflow tank? Could have a small leak using water, and then getting air in?? Does the gauge just go up to hot and stay there or will go up quickly and down quickly possibly as the result in airlock. I always use genuine thermstats for commy as they are only about $8 or so so well worth it.

If all else fails I would be looking for a small leak, pressure test when stone cold and for a few hours will generaly show something if its leaking.

Im starting to think it was last time too, even though they reckoned the levels were fine. Nope, I don't think they were. Even after I told them to keep an eye on it last time. It gets hot and stays up there, not fluctuating so it wasn't really a problem with air being in the system like you expect when the gauge moves all over the place, so ruled that out pretty early.

Turned up this morning and needed about 6L of water (didnt worry about coolant just yet) to fill the system. Big surprise there, same as last time, so now it kinda narrowed it down to the cause as something causing the coolant loss. Had a good look around, no signs of leaks from welch plugs like can happen, hoses were ok, no other visual signs anywhere. Pulled the waterpump anyway to have a look and it had some damage to the fins and a fair bit of cavitation, but looks like it still would have been working ok. Thermostat I put in previously was fine too, double checked it. Put things back together and started to bleed the system so I could pressure test the cooling system and see if there was a leak somewhere. Soon as I started bleeding it the coolant started showing nice signs of a blown head gasket. Nice and frothy when running it at revs, soon as I cracked the bleeder it was pushing coolant out the top maybe 6 or 7 inches high! It wasn't like that last time, just the usual bubble out the top (like a water bubbler), so it has certainly gotten worse.

Still, they got it hot again and finished off the gasket I reckon. I think the problem was probably the head gasket right from the start, probably before we even looked at it awhile ago, managed to get a little more info out of them and it's been doing weird overheating things for about 12 months now. The thermostat was stuck when I replaced it last time after it presented with the same signs, suddenly getting hot, poor circulation, etc. It was pretty low on coolant then too, but given it had got fairly hot and the thermostat was stuck, combined with a nice little white trail along the passenger side frame rail, figured it probably pushed quite a lot out of the overflow and started with the most simple (and cheapest) thing to fix. Bled up ok, no other signs of the gasket being gone, but did ask them to keep an eye on the coolant level and let me know if it dropped or needed any added to fill it.

I figure it has probably had a bit of a gasket leak for some time, either it would pressurise the cooling system and spit coolant out the overflow, or it was sending a little out the tailpipe. The 6 or 7 week window was how long it was taking before the cooling system was so low on coolant it simply couldn't keep the car cool any longer, hence the big sudden overheating issue and the circulation problems. Certainly finished off the gasket last night though, no coolant in the oil yet, but I reckon there will be in the next couple of days. Certainly loads of pressure in the cooling system now and a nice drip from the exhaust, plus pressure test the cooling system and it slowly bleeds off pressure. The amount of coolant running out the exhaust is pretty small, about the same as a condensation drip, but it still does it even when up to temp, so all things combined, gasket is gone for sure.

I guess you can only ask them to report back if there are any issues and leave it up to the customer. Even asked them to drop it back a week later just to double check the levels but heard nothing and assumed things were ok.

Thanks for the help guys. I guess, couple overheating problems plus over 180,000 on the clock, blown gasket isn't that abnormal, especially if they aren't keeping an eye on the levels.